[vtk-developers] vtk performance - issue 1 - OpenGL state

[Hank Childs]

> 
> This first issue has to do with unnecessary calls to set 
> OpenGL state (please excuse me if this terminology is incorrect,
> I'm not an OpenGL expert).

Just a data point for everyone out there.  Stanford has a project called
WireGL (http://www.graphics.stanford.edu/software/wiregl/) that "is an
active research project .. to explore cluster rendering systems."
Essentially, you can use the WireGL library instead of OpenGL and it will
handle issues for rendering to tiled displays.  Its interface is exactly
the same as OpenGL's.

The point is that they wrote their own OpenGL state tracker.  They have
run VTK apps using WireGL and they have often said that those apps run
faster on tiled displays (with WireGL) than on normal terminals (wo
WireGL).  I spoke to Greg Humphries (the author) and he told me that it is
all due to the state tracker that eliminated redundant calls.

Again, just a data point.  All of the GL calls could go through a
vtkOpenGLStateTracker.

-Hank

____________________________________________________________________________

Hank Childs
MeshTV
Lawrence Livermore National Laboratory

phone: (925) 422-4035
email: childs3 at llnl.gov